<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    
    <script>
        var a = [1, 2, 3, 4, 5]
        var b = [6, 7, 8, 9]

        var c = a.concat(b);
        console.log(c);
    </script>

    <script>
        var container_arr = [];
        for(var i = 0,count = 0 ; i < 5; i++){
            var arr = [];
            for(var k = 0 ; k < 5 ; k ++){
                // 建立基本结构
                count ++;
                arr.push(count);
                // 输出内容
                if( k <= i){
                    document.write(count + "&nbsp;&nbsp;");
                }
            }
            container_arr.push(arr);
            document.write("</br>")
        }
        console.log(container_arr);
    </script>


    <script>
        var container_arr = [];
        // 建立五个数组
        for(var i = 0,count = 0 ; i < 5; i++){
            var arr = [];
            for(var k = 0 ; k < 5 ; k ++){
                // 这个内层循环会执行 5 * 5 次
                count ++; //count会从1 ~ 25
                arr.push(count);
            }
            // 5个数组都放在这个容器数组里
            container_arr.push(arr);
        }
        // 5*5二维数组
        console.log(container_arr);
    </script>
</body>
</html>